Knee osteoarthritis (OA) is one of the most prevalent musculoskeletal
conditions worldwide, affecting hundreds of millions of people and
representing a leading cause of chronic pain and physical disability. As
populations age and rates of obesity rise, the burden of knee OA continues to
grow, placing enormous pressure on healthcare systems and diminishing
quality of life for countless individuals. Conventional treatments — ranging
from analgesics and physiotherapy to corticosteroid injections and, ultimately,
total knee replacement surgery — each carry limitations in efficacy,
tolerability, or cost. Against this backdrop, APOS therapy has emerged as an
innovative, non-invasive biomechanical approach that aims to address the
root mechanical causes of knee OA pain rather than merely managing its
symptoms.
What Is APOS Therapy?
APOS (All Phases of Stride) therapy is a personalised biomechanical
rehabilitation system developed in Israel in the early 2000s. At its core, the
system consists of specially designed convex-soled shoes, each fitted with two
independently adjustable pods positioned beneath the heel and forefoot.
These pods create a controlled degree of instability during walking,
challenging the neuromuscular system to continuously adapt and rebalance.
Unlike conventional orthotics, which provide rigid mechanical correction, the
APOS platform engages active muscle recruitment throughout every phase of
the gait cycle — hence the name.
The device is configured by a trained clinician following a detailed
biomechanical assessment. Using force-plate gait analysis, the clinician
identifies abnormal loading patterns, joint malalignment, and muscle
compensation strategies unique to each patient. The pods are then calibrated
in position to offload the most affected compartment of the knee joint —
typically the medial compartment, which bears the brunt of load in
varus-aligned knees — while simultaneously stimulating improved
neuromuscular control. Patients are instructed to wear the shoes for a
prescribed period each day, typically starting at around 30 minutes and
gradually increasing as tolerated.
The Biomechanical Rationale
The pathomechanics of knee osteoarthritis are well-established. In the
majority of patients, the medial compartment of the knee is subjected to
disproportionate loading, a phenomenon quantified by the knee adduction
moment (KAM) during gait. Elevated KAM is strongly associated with medial
cartilage degradation and disease progression. Traditional lateral wedge
insoles attempt to reduce KAM by shifting the ground reaction force laterally,
but clinical evidence for their long-term effectiveness has been inconsistent.
APOS therapy targets the KAM and broader gait dysfunction through a
dual mechanism. First, the precise positioning of the pods acts similarly to a
wedge insole in redistributing joint loads. Second — and more distinctively —
the instability introduced by the convex pods prompts continuous
proprioceptive feedback, training the periarticular muscles to better stabilise
the knee throughout the gait cycle. This neuromuscular re-education may
yield benefits that persist beyond the period of device use, potentially
modifying gait patterns in a durable way. There is also evidence that the
perturbation-based loading produced by the APOS platform can stimulate
cartilage metabolism, though this remains an area of ongoing investigation.
Clinical Evidence
A growing body of clinical research supports the effectiveness of APOS
therapy for knee OA. Several randomised controlled trials (RCTs) and
prospective cohort studies have demonstrated meaningful improvements in
pain, function, and quality of life. A landmark study published in the journal
Arthritis Care and Research found that patients undergoing APOS therapy
experienced significant reductions in pain intensity and improvements in self-reported physical function compared to control groups. Gait analysis data
corroborated these subjective outcomes, showing measurable reductions in
KAM and improvements in walking speed and step symmetry.
Longer-term follow-up studies have suggested that the benefits of APOS
therapy are maintained well after active treatment has concluded, lending
credence to the hypothesis that the intervention produces lasting
neuromuscular adaptations rather than simply offloading the joint during
device use. Some research has also indicated that APOS therapy can delay or
reduce the need for surgical intervention in patients who might otherwise be
considered candidates for knee replacement. This finding has significant
implications for healthcare resource utilisation, particularly given the costs,
risks, and extended rehabilitation associated with arthroplasty.
Advantages Over Conventional Approaches
APOS therapy offers several practical advantages that distinguish it from
other conservative treatments. Because it is integrated into a walking shoe
worn during routine daily activity, the therapy requires no dedicated exercise
sessions, gym attendance, or significant time commitment beyond the
prescribed wearing period. This is a meaningful advantage for older adults or
those with comorbidities that limit participation in structured exercise
programmes. The non-pharmacological nature of the therapy also means it is
free of the gastrointestinal, renal, and cardiovascular risks associated with
long-term non-steroidal anti-inflammatory drug (NSAID) use — a major
concern in the OA population, which skews elderly.
Furthermore, the individualised calibration of the APOS device ensures
that treatment is tailored to each patient’s specific biomechanical profile,
rather than applying a one-size-fits-all solution. This personalisation is
particularly valuable in a condition as biomechanically heterogeneous as knee
OA, where patient phenotypes vary considerably in alignment, muscle
strength, gait pattern, and disease severity.
Limitations and Considerations
Despite its promise, APOS therapy is not without limitations. The upfront
cost of the device and associated clinical assessments can be a barrier for some
patients, and reimbursement by insurers and public health systems varies by
jurisdiction. The therapy requires access to a trained APOS clinician and
specialised gait analysis equipment, which may limit availability in rural or
under-resourced settings. Some patients may also find the instability of the
convex pods challenging initially, particularly those with significant balance
impairment or peripheral neuropathy, although protocols are designed to
introduce perturbation gradually.
Critics have also noted that while the existing body of evidence is
encouraging, many studies have been conducted by groups with ties to the
APOS system’s developer, raising questions about potential bias. Independent,
large-scale RCTs with robust blinding and long follow-up periods are needed
to definitively establish the therapy’s place in the OA treatment hierarchy.
Head-to-head comparisons with other active interventions, such as structured
physiotherapy or lateral wedge insoles, would also be valuable.
Knee osteoarthritis remains a formidable challenge in musculoskeletal
medicine, and the search for effective, safe, and accessible treatments
continues. APOS therapy represents a genuinely novel contribution to this
landscape: a personalised, biomechanically-grounded intervention that
addresses the mechanical underpinnings of the disease rather than simply
dampening its symptomatic expression. The available clinical evidence is
promising, suggesting meaningful and durable reductions in pain and
improvements in physical function, alongside the potential to delay surgical
intervention. As independent research matures and access to the technology
broadens, APOS therapy may well secure a firm and important role in the
multidisciplinary management of knee osteoarthritis — offering patients a
path toward greater mobility and independence without the risks of surgery or
long-term medication use.